I was trying to find a sub enclosure to fit the trunk without having to drill anywhere and I see many for the w204 designed to fit directly against the rear seats and spread the width of the trunk to secure it. Was wondering if we have similar trunk dimensions on the w207 to accomodate this.

I would say yes to VERY similar dimensions in regards to end-to-end length from the strut tower to the other strut tower, for the W204 coupe, not sedan. The small ledges & trunk sides that the enclosure secures to, may differ. I can confirm that the front W204 aftermarket strut tower braces fit the C207. I have not seen the rear fitted to a C207, but logic would lead to this assumption. My suggestion is to find the car the box is meant for and go check it out at a dealership to get some measurements. OR ask the W204 forum to acquire this for you..